Method of reducing ores.



0. PRIGK.

METHOD OF RBDUGING ORBS. APPLICATION FILED APR. 4, 1910.

1,010,490. Patented 1360.5, 1911.

.Wegen ercr 2 5.

Il Il' OTTO I FRICK, OF STOCKHOLM, SWEDEN.

METHOD l0F REDUCING ORES.

Specification of Letters Iatent.

Patented Dec. 5, 1911.

Application filed April 4, 1910. Serial No. 553,428.

To all 'whom tmc/gl concern:

Be it knownthat I, Orro Fmox, a subject of the King of Sweden, residing at Stockholm, Sweden, have invented certain new and useful Improvements in the Methods of Reducing Gres; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to letters or gres of reference marked thereon, which form a part of this specification.

@My invention relates to amethod of reducing ores, more especially to the reduction of iron ores in the blast furnace, and has for its object to economize the heat units and return a portion of the heat contained in the gases resultin from the reduction Aback into the reductlon zone of the furnace, thereby saving considerable fuel, or reducing the cost of a large part of the fuel by enabling the use' of cheaper grades lof fuel, or both.

- The accompanying drawing is a diagram of the various structures necessary for the carrying lout of the invention.

Referring to said drawing,'the reduction or blast furnace 1, is of any'desired type of construction. The gases pass from the top of the furnace 1, or from the charge, by pipe 2 to a heat exchanger 3, from which latter they pass by a pipe 4 to a water chamber, Theisen, or other gas` washer- 5, thence through' pipe 6 to a compressor 7 that is operated by an engine 8, and which discharges by means of pipe 9V backl into the heat exchanger?) to re-absorb heatleft inthe exchanger by said gases. The compressed gases then pass to a line pipe 10, through aout-off valve 11, to a heated hot Y blast stove A, thence through pipe 13, valve 14 and pipe 15 back into the blast furnace. A second portion of the gas passes by pipes 10 and 16 through valve 17 to a regenerator 18, and a third portion by pipe 19, through valve 20 to a regenerator 21.

The gas is burned in both of the regenerators 18 and 21 with access of air, and the products of combustion therefrom -either escape into the atmosphere or are conducted, as is customary, beneath the boilers for generating the steam for the plant to a com- 4 mon stack. A ,portion of the gas passes through the pipes 16 and 19, andk valve 22 to the heated regenerator 23, is heated in this regenerator and passes by pipe 25 and valve 24 to the hot blast stove B. At the same time air is forced through the hot re-l generator 26 and valve 27 and pipe 28 for 'the combustion of the heated gas in the hot 32 to the hot blast stove A. At the samek time air is passed through valve a, the regenerator21, and valve 31 to provide hot air for the combustion of the gas in the hot blast stove A. A portion of the gas passes through the pipes 10 and 16, and

valve 34 to regenerator 23 to heat the same, (valves 22, 24, 27 and air valve f being closed,) and through pipe 19 and valve 35 to the air regenerator 26. Air for combustion is supplied from the air main through valves Z and4 f. These two regenerators discharge their products of combustion either into the atmosphere, or beneath the boilers, as is found mo-st expedient.

The operation will no doubt be evident from what has been said. The furnace is placedv in operation, or blown in in the usual manner, and after that-I take all' or the greater portion of the gas generated in the blast furnace, except such as may be required to heat any blast that mayr be used for carrying out eiiiciently the operations in the` blast furnace, cool the gas, clean it,-

compress it, thereby heating it to a certain extent, return it to the heat exchanger wherein it was cooled and wherein it reabsorbs heat previously given up on its passage to the compressor, and send some of the gas under pressure through one of the hot blast stoves, Aor B, back into the furnace. SomeJ of the gas is kutilized in heating regenerators 18, 21, 23 and 26, 'in

,order to pre-heat the gas to be burned within the hot blast stoves for -heating the stoves to a high temperature in order to heat thatJ portion of the compressed gas on its Way back into the blast furnace 1. These gases are preferably heated to a temperature. sufficient to melt the stock.

The capacity of the compressor is preferably such as to take care of a quantity of gas several times the volume of that produced by the furnace in a unit of time, for example in one second, so as to maintain through the furnace a strong and constant circulation of gas, while any excess or accumulation of gas due to the continuous working of the blast furnace is utilized for heating the regenerators 2l, 18, 23 and 26, as well as the hot blast stoves A and B.

Instead of heating the regenerators 21, 18, 23 and 26 by means of blast furnace gas .exclusively, I may pass some blast furnace gas into the regenerators together with the producer gas, either separately, or preferably by taking the cooled blast furnace gas from pipe 6 through a cut-off valve 36, a back pressure valve 37, and a centrifugal pump 38, through a separate portion 3 of the heat exchanger 3, thence by pipe 39 to a gas producer 40, by pipe 41 and valve 43 to pipe 16.

42 and 43 are cut off valves, so that by closing valves 43 and 36 and opening valve 42 the producer can be cut out of circuit.

The nature of the charge, conditions of operation and capacity of the various heat storing and producing elements, being properly selected, by the use of the gas producer 40 I am enabled to successfully run a blast furnace, after it has been blown in in the usual way, without air through the twyers. However, under certain conditions it is perhaps not convenient or expedient for practical reasons, to work wholly without air, and in that event a certain quantity of air or hot blast must be supplied through the twyers. At the same time it is quite expedient to vary the quantity of air supplied to the blast furnace from zero to a maximum, according to the conditions under which we are operating. In order to explain these conditions I will state that at present about 900 kilos of carbon are required for every ton of pig produced. 300 kilos of carbon are necessary for the reduction of the ore, the remaining 600 kilos of carbon go to supply the heat required for heating the charge'and maintaining the body of metal Huid. By my process I am enabled to reduce the quantity of carbon used, z'. 6.,.that quantity which goes to heating the charge and maintaining the body of metal fluid, and this saving of fuel varies considerably in accordance'with the nature of the charge and the conditions under which the operations are carried out. I have succeeded in reducing this amount from 600 Ito 300 kilos of carbon, showing a savingv in the cost of total carbon in the charge of thirty-three and one third per cent.; however, this saving may become still greater when I enrich the blast furnace gas used for heating purposes by producer gas, for the reason that the fuel used in the produccris a much cheaper grade of fuel than that used in the furnace, so that the actual carbon contentI in the charge may be reduced to about 300 kilos per ton of pig, the rest of the carbon being supplied from a cheaper grade of material through the producer, consequently reducing the cost of the carbon required for producing a ton of pig to less than two thirds of the present cost. In this case the amount of carbon used exceeds 300 kilos per ton of pig. It is of course still preferable, but not necessary, that the gas be of sufficient temperature to melt the charge in the furnace. When the temperature of the re-heated gas is such as not to be able to melt the charge in the furnace, then sufficient air must be supplied together with thecarbon for combustion, to furnish the additional amount of heat required. These conditions are present when the regenerators 18,21, 23 and 26 are omitted from the plant for the sake of economy of construction, o-r otherwise, in which case the compressed, reheated gas is sent alternately through the hot blast stoves A and B, either in connection with the producer gas, or without it, and to this end valves 44 and .45 are opened and valves 20, 27, 3l and 35 are closed, whereby the hot blast stoves are fed directly from pipes 16 and 19; regenerators 21 and 26 are cut out of circuit; at the same time pipes 25 and 25a are disconnected in front of the valves 32 and 24. The valves 32 and 24 are closed, when the blast furnace gas is passed through the hot blast stove A, for the purpose of heating it, as is customary, and is well understood in operating ordinary hot blast stoves when reversed.

That portion of the blast furnace gas which is maintained incircuit through the furnace passes through the heated blast stove A or B, pipe 15, to the furnace, where it gives off its excess of heat, and is used in conjunction with the carbon and air for melting the charge.

When plants are located at places of cheap water power for producing electricity, the gas, after leaving the hot blast stove, A or B, is electrically heated, either in the furnace itself, which isthen preferably an electric furnace. or by being passed through an electric heater 48, which may or may not contain carbon as a heating medium, over and through which t-he gas, or a portion of the gas, circulates, the remainder passing through theby-pass 49. If the heating medium is carbon the gas is enriched; if it is an inert, material, as a refractory material,

the gas is simply heated. When the gas is electrically heated, or, as the case may be,

' V1. The method of reducing ores, which lcomprises vestablishing reduction in a reduction furnace, maintaining a continuous circulation through said furnace of a portion of the gas produced in the furnace, heating a i. second portion of said gas by heat derived from a third portion of said gas, burning it With air heated by another portion of said gas and heating the gas circulating through the furnace by heat derived from said burning.

2. The method of reducing ores, Which comprises establishing reduction in a reduction furnace, maintaining a continuous circulation through said furnace of a portion of the gas produced in the furnace, enriching and heating a second portion of said gas by heat derived from a second portion of the enriched gas, burning the heated enriched gas with air heated by heat derived from a third portion of the enriched gas and utilizing the heat of such burning to heat that portion of the gas circulating through the furnace. v

3. The method of reducing ores, Which comprises establishing reduction inV a reduction furnace, maintaining a continuous circulation through said vfurnace of a portion of the gas produced in the furnace, heating a second portion of said gas by heat derived from a third portion of said gas, burning it with air heated by another portion of said gas, heating the gas circulating through the furnace by heat derived from said burning, and finally electrically heating said gas before passing into the furnace.

4. The method of reducing ores, Which comprises establishing reduction in areduction furnace, maintaining a continuous circulation through said furnace of a portion of the .gas produced in the furnace, enriching and heating a second portion of said gas by heat derived from a second portion of the enriched gas, burning 'the heated enriched gas with air heated by heat derived from a third portion of the enriched gas, utilizing the heat of such burning to heat that portion of the gas circulating through the furnace, and`finally electrically heating said gas before passing into the furnace.

5. The method of reducing ores, which comprises establishing reduction in a reduction furnace, maintaining a continuous circulation through said furnace of a portion of the gas produced in the furnace, heating a second portion of said gas 4by heat derived from a third portion of said gas, burning it with air heated by another portion of said gas, heating the gas circulating through the furnace by heat derived from said burning and finally electrically heating and simultareously enriching said gas before passing into the furnace.

6. The methodl of reducing ores, which comprises establishing reduction in a reduction furnace, maintaining a continuous circulation through said furnace of the gas produced, and heating said gas by heat derived from a second portion of furnace gas, then electrically heating and enriching said gas in carbon, outside the furnace during its circulation. I

7. The method of reducingl ores, which comprises establishing reduction in a reduction furnace, maintaining a continuous circulation through said furnace of the gas produced, heating said gas by heat derived from a second portion of furnace gas, and electrically and simultaneously enriching said gas in carbon outside the furnace, during its circulation, and decreasing the quantity of carbon in the charge below that required under ordinary conditions during the progress of reduction to a minimumquantity. i

8. The method of reducing ores, which comprises establishing reduction in a reduction furnace, maintaining a continuous circulation through said furnace ofy the gas produced, and electrically heating and simultaneously enriching said gas in carbon outside the furnace during its circulation, decreasing the quantity of carbon in the charge, below that required under ordinary conditions, during the progress of reduction to a .minimum quantity, and maintaining the total carbon in the processbelowl that required under ordinary conditions.

9. rlhe method of reducing ores, which comprises establishing reduction in a reduction furnace, maintaining a continuous circulation through said furnace of the gas pro-- duced,l and during its circulation washing and thereby cooling said gas and compressing it, then re-absorbing some of the heat given up in cooling, heating the gas and returningit to the furnace.

l0. The method of reducing ores, which comprises establishing reduction in a reduction furnace, maintaining a continuous circulation through said furnace of the gas produced, Washing and thereby cooling said gas, compressing it, re-absorbing some of the heat given up in cooling, heating the gas, returning it to the furnace during its circulation and enriching the gas at one or more points outside the furnace.

11. The method of reducing ores, Which comprises establishing reduction in a reduction furnace, maintaining a continuous circulation through said furnace of a portion of the gas produced, and heating said gas outi' side the furnace, during its circulation by a second portion of the gas produced by the charge enriching that portion of the gas that circulates through the charge with carbon, and enriching with carbon the sec- 0nd portion of the gas for heating the rst portion.

In testimony that I claim the foregoing as my invention, I have signed my name in presence of two subscribing Witnesses.

- OTTO .F RICK. Witnesses:

HENRY ORTH, J r., A. M. PARKINS. 

